Yes, the light is blinking on and off- the alarm is very loud and continues until we unhook the battery terminal (I think that's what they are called) from the battery. As soon as we try to hook up the new battery, the alarm goes off and the car won't turn over- all the lights light up in the panel, but it's as if the ignition is disengaged.

I am almost positive this is factory-installed- my father purchased the car and he never included any extras- he stayed as far away from tinkering with cars as possible! This alarm is doing everything- honking the horn, the police siren sound (whew, whew, whew). To be honest, I can't say 100% it was factory-installed, but I'm reasonably certain it was. I'm sure there's some way for an individual to switch out a battery without not being able to drive the car, because that's what happened. The original Interstate battery was jumped, and AutoZone's tests came up Bad Battery. So we bought a Duralast. Once we tried to connect the terminals to the new battery, the alarm started going off. I tried pushing the red alarm button on my key chain, which shut it off. But then every time we tried to hook up the battery, the alarm went off again.

Not sure. May have hooked up the negative first or the positive. Would that make a difference?

So I need to hook up the positive first, then the negative. If I do this and the ignition still won't turn over, should I contact the manufacturer?